Keiichi Yano

Design and characteristics of a newly developed cavity-up plastic and ceramic laminated thin BGA package

The key requirements for a package are high electric and thermal performance, thinness, light weight, small size or high assembly density, and low cost. Plastic packages are superior in terms of electrical performance and cost whereas highly thermally conductive ceramic packages are superior in terms of thermal performance, weight, and size. However, these conventional plastic or ceramic packages cannot simultaneously satisfy all the requirements A new cavity-up plastic and ceramic laminated package (PCLP) has been developed that not only has superior electrical and thermal characteristics simultaneously without a heat sink, but also a thin profile and small size and is cost-effective. For example, the frequency range applicable to the PCLP exceeds 500 MHz, the maximum power dissipation is 4 W under natural convection, and the thickness is less than 2 mm. The PCLP is composed of two substrates: an electrically conductive plastic substrate and thermally conductive ceramic substrate. The plastic substrate, made of liquid crystal polymer (LCP) and copper, forms a flexible printed circuit (FPC). LCP is a suitable material since it has low water absorption, low dielectric constant, and low dielectric loss. The ceramic substrate is cofired tungsten-metallized aluminum nitride (AlN). It has high thermal conductivity and its coefficient of thermal expansion (CTE) is close to that of silicon. The AlN substrate also supports mechanically both the FPC and the semiconductor chip. The package is made using simple processes: both FPC and AIN substrate are single insulation layers; interconnection technologies are simple, for example, screened bump interconnection and lamination; and a conventional pattern formation is used, for example, screen printing. The measured electrical resistance is 450 m/spl Omega/ (line length 14.7 mm, width=50 /spl mu/m), which was about 1/10 of that for a simple ceramic cofired package of the same dimensions with a tungsten conductor. The measured thermal resistance is 10.8/spl deg/C/W under natural convection without a heat sink. In this paper the PCLPs design concept, configuration and performance characteristics are reported.

A thin and low thermal resistance aluminum nitride BGA package for high speed DSP devices

Low thermal resistance and high TCT (temperature cycle test) reliability have been attained by thin AlN BGA package structure. High speed signal transmission for multimedia DSP (digital signal processor) has been analyzed by computer simulation. The package has 0.6 mm body thickness, which is 1/3 of ordinary ceramic packages. A low thermal resistance of 4.8 /spl deg/C/W has been attained without a heat sink and with no air cooling while mounted on a PWB having 4 conductive layers. Scattering parameters were measured up to 9 GHz and applied to 250 MHz clock signal simulation. No deterioration of signal waveforms was observed during the simulation. The effects of package thickness and package size have been discussed from the thermal resistance and TCT reliability point of view. Thicker and larger package size provided lower thermal resistance. The developed package thickness and size (35/spl times/35 mm) have been determined by taking into account the application field of mobile PCs (personal computers) and through simulation. The package thickness versus TCT reliability has been discussed, and then the TCT has been carried out under an assembled condition on a PWB, and MTTF of 1 k cycles has been derived.

An organic and ceramic laminated BGA package with high thermal and electrical performance characteristics

A new structural face-up LSI package has been developed. The package shows low thermal resistance without a heatsink and low inductance, capacitance, and resistance values. The package is thin enough for portable multimedia equipment applications, with a thickness of 0.5 mn (not including ball height). The measured thermal resistance was 11/spl deg/C/W under natural convection without a heatsink. The simulated inductance and capacitance were 6.7 nH and 1.1 pF respectively, and measured resistance was 520 m/spl Omega/ (line length=14.7 mm, width=60 /spl mu/m). The package consists of a resin film and a ceramic substrate. The film is a liquid crystal polymer (LCP) and the substrate is aluminum nitride (AlN). LCP is a suitable material for buried-bump interconnection technology (B2it/sup TM/). AlN has high thermal conductivity and its coefficient of thermal expansion (CTE) is close to that of silicon. Both materials were laminated by an adhesive agent. This material combination provides a thin structure, low thermal resistance, and low LCR which are suitable for portable multimedia electrical equipment. This paper reports the configuration and performance characteristics of this newly developed package.